Cartography is visual argumentation: a map succeeds when its reader grasps the intended message quickly and is not misled on the way. The craft rests on a handful of principles — visual hierarchy that ranks what matters, figure-ground separation, restrained colour with perceptual logic, legible typography, and honest encoding of data. Software defaults produce maps; these principles produce communication.
Hierarchy and figure-ground
Every map element competes for attention; design is deciding the winners. The thematic subject should dominate through stronger colour, weight or contrast, while base information — roads, boundaries, labels — recedes into a quiet supporting cast. Squint at a draft: what pops first should be the message.
Figure-ground techniques (muted basemaps, subtle vignettes, desaturated context) lift the subject off the page. The commonest failure is democratic emphasis — everything bold, therefore nothing readable.
Colour and symbology with logic
Colour carries meaning, so it must follow data structure: sequential ramps for ordered magnitudes, diverging ramps around a meaningful midpoint, qualitative palettes for categories. Perceptually uniform ramps (the viridis family, ColorBrewer sets) prevent the false boundaries rainbow ramps invent, and colour-vision-safe choices are professional courtesy, not garnish.
Symbol sizing should scale with quantity honestly; classification choices (breaks, counts) shape the story and belong in the metadata, not hidden.
Typography and honest maps
Labels are the map’s voice: hierarchy through size and weight, placement that binds label to feature unambiguously, halos used sparingly, and ruthless pruning — every label must earn its clutter. Marginalia (scale, sources, date, projection) is credibility infrastructure.
Above all, honesty: no truncated axes of the map world — no misleading class breaks, no projections that inflate the argument, no data mapped beyond its accuracy. A beautiful map that misleads is a well-dressed lie.